Device for uniform distribution of material over a horizontal cross-sectional area of a vertically extending zone



Oct. 9, 1956 J- PUHR-WESTERHEIDE 2,765,588 DEVICE FOR UNIFORMDISTRIBUTION OF MATERIAL OVER A HORIZONTAL CROSS-SECTIONAL AREA FiledOct. 20, 1952 OF A VERTICALLY EXTENDING ZONE 2 Sheets-Sheet 1 INVENTORJurgen Puhr-Wrzfarheide ATTORNEY 1956 J. PUHR-WESTERHEIDE 2,765,588

DEVICE FOR UNIFORM DISTRIBUTION OF MATERIAL OVER A HORIZONTALCROSS-SECTIONAL AREA OF A VERTICALLY EXTENDING ZONE Filed Oct. 20, 19522 Sheets-Sheet 2 INVENTOR dzzrgen abr- Wser/zeia/e ATTORNEY DEVICE FORUNIFORM DISTRIBUTION OF MA- TERIAL OVER A HORIZONTAL CROSS-SEC-IOfiligAL AREA OF A VERTICALLY EXTENDING Jurgen Puhr-Westerheide,Oberhausen, Germany, as-

signor to The Babcock & Wilcox Company, New York, N. Y., a corporationof New Jersey Application October 20, 1952, Serial No. 3155798 Claims.(Cl. 519) T his invention relates to apparatus for distributing materialsubstantially uniformly over a horizontal crosssectional area of avertically extending zone and, more particularly, to a centrifugalspreader of uniform effective radius operated by driving means effectiveto periodically vary the angular velocity of the spreader.

While not limited thereto, the invention is particularly adapted toarrangements for cleaning the gas contacted surfaces of tubular heatexchangers. In such exchangers, heat transfer may be effected by heattransfer from relatively hot combustion gases to metal tubes carryingrela tively cooler liquids or vapors. Depending upon the characteristicsof the fuel burned to produce the hot gases and upon the efliciency ofcombustion, the hot gases flowing over the tubes will carry a greater orless amount of fly ash and other solids in suspension, and a proportionof these solids are deposited upon the gas contacted tube surfaces.

The thus deposited solids reduce the efiiciency of heat transfer fromthe gases to the tubes, and the deposits, if not removed, may build upto an extent sufficient to bridge inter-tube spaces and at leastpartially block the gas passes. Accordingly, it is desirable to removethe deposited solids either at regular intervals or whenever thedeposits have built up to a predetermined extent.

Soot blowing is effective in dislodging the finer deposited solids whichhave not adhered to the tube surface, but is not effective to removesolidified slag from the surfaces. Various arrangements have beenproposed for dislodging the adhering solids, and one effective method isto discharge relatively hard pellets, metal balls, or gravel over thegas contacted tube surfaces. The pellets may be forcibly discharged fromnozzles against the tube surfaces or may be distributed above the tubesurfaces to fall by gravity thereover.

in the latter case, the pellets are discharged from a centrifugaldistributor rotatable about an upwardly extending axis locatedsubstantially centrally of a horizontal cross-sectional area over whichthe pellets are distributed to fall through a substantially verticallyextending zone in which the tubular heat exchanger is arranged. In orderto secure substantially uniform distribution of the pellets over thehorizontal area, the distributor is preferably formed with an involuteperiphery so that varying redial discharge velocities are imparted tothe pellets for uniform distribution thereof over the horizontal area.The pellets may be fed to the distributor through a feed conduit coaxialwith the axis of rotation.

Whiie the involute distributor is effective in obtaining substantiallyuniform distribution of the pellets over the horizontal cross-sectionalarea, it is subject to mechanical difficulties because of itsnon-circular form. Due to the unequal radial location of points on itsperiphery, the involute distributor is not in dynamic balance, thusintroducing undesirable stresses on its mounting and drivingarrangement. This lack of dynamic balance can be corrected by the use ofequalizing or balancing weights attached to the distributor. However,determination of tates atent the mass of these weights and theirrelative position necessitates a time consuming balancing operation involving the testing of every involute distributor before the latter isplaced in operation.

In accordance with the present invention, a uniform distribution of thepellets over the horizontal crossectional area is effected without thenecessity for such dynamic balancing by utilizing a distributor having acircular periphery concentric with its axis of rotation, and drivingthis distributor at periodically varying angulaf velocities. The drivingarrangement is so designed that the time period of operation at anyangular velocity is proportional to the value of the angular velocity,thus taking into account the greater area to be covered at larger radiiof distribution. At the very low angular velocities the pellets have avery low or substantially zero radial velocity and follow over thecentral core of the distribution area. With increasing angularvelocities, the pellets are given increasing radial velocities so thatthey are distributed over circular strip areas of increasing radii. Witheach increase in distribution radii, the area to be covered increases asan exponent of the radius of distribution. Hence, the number of ballsdistributed must be increased with increasing radii of distribution toachieve uniform distribution per unit of area.

More particularly, the distributor comprises a conical element to whichthe pellets are fed through a pipe or conduit extending coaxially withthe axis of rotation. The distributor is rotated by a constant speedprime mover, such as a constant speed electric motor, which drives thedistributor through an infinitely variable or stepless speed changingtransmission of the type having a control lever movable to vary theoutput speed of the transmission. This control lever is provided with acam follower engaged by a rotatably mounted cam driven at a uniform andconstant angular velocity by the constant speed motor. The cam is sodesigned that the transmission control lever is held in a given speedselector position for a time period proportional to the particularoutput speed of the transmission.

For an understanding of the invention principles, reference is made tothe following decsription of a typical embodiment thereof as illustratedin the accompanying drawing. In the drawing:

Fig. 1 is a central, vertical sectional view through a pelletdistribution apparatus embodying the invention;

Fig. 2 is a somewhat schematic elevation view of the driving mechanismfor the pellet distributor; and

Fig. 3 is a plan view of one form of driving mechanism useful with theinvention; and

Fig. 4 is a side elevation view of the driving mechanism shown in Fig.3.

The distributor 10 of the invention is mounted, for rotation about asubstantially vertical axis, immediately beneath the roof 11 of asubstantially vertically extending zone, such as a vapor generator gaspass containing one or more tubular heat exchangers (not shown). Forexample, 11 may be the roof of the gas pass shown in Fig. 4 of mycopending application Serial No. 315,304, filed October 17, 1952.

Distributor 10 is designed to distribute pellets, for example steelballs having a diameter of 3 mm., uniformly over a horizontalcross-sectional area of the vertically extending zone. These balls aredelivered to distributor 10 through a pipe or conduit 12 extendingcoaxially With the axis of rotation of distributor 10.

Pipe 12 is mounted to rotate about its axis in anti-friction bearings 13supported on a framework 14 mounted on the supporting elements 16 forroof 11. The pipe 12 extends through a jacketing pipe 17 mountedvertically through roof 11, and is guided in a bearing 18 secured in thelower end of a gear housing 15.

Within gear housing is disposed a bevel gear secured on pipe or conduit12, to rotate therewith, by means of a conical clamping sleeve 21 and athreaded cap 22. Bevel gear 20 is rotated by a bevel pinion 25 meshingwith the bevel gear and comprising the output gear of a drive mechanismgenerally indicated at and described more fully hereinafter. Drivemechanism 30 is suitable supported on the framework 14.

At its lower end, pipe 12 is provided with a downwardly convergingfrusto-conical pellet delivery nozzle 23. Telescoped onto the lower endof pipe 12, and welded thereto, is a tubular axle or mounting member 24for distributor 10.

In the illustrated embodiment, distributor 10 comprises a shallowconical disk having radial ribs 26 connecting the disk to tubular member24. At the apex of disk 10 is a distributing cone 27, and in the spacebetween the base of cone 27 and the inner ends of ribs 26, disk 10 isformed with holes 28 of somewhat larger diameter than that of thepellets. These have the function of distributing the pellets to the zoneimmediately beneath the apex of disk 10 and substantially on the axis ofrotation.

Alternatively, the distributor may comprise one or more radiallyextending tubes of equal radial length and extending either horizontallyor at a small angle to the horizontal downwardly and outwardly.

The driving arrangement 30 for distributor 10 will be best understood byreference to Fig. 2. Output shaft 31 of a constant speed electric motoris connected by a coupling 32 to the input shaft 33 of an infinitelyvariable or stepless speed-change transmission 40. As schematicallyindicated at 34, input shaft 33 is connected to drive a rotatable cam 50at a uniform substantially constant speed.

Transmission is provided with a speed selector and control leverpivotally mounted at 41 on the casing of transmission 40 and constantlybiased to the low speed position by a spring 42 connected between oneend of lever 45 of the transmission housing. The other end of lever 45carries a cam follower 43 continuously biased against the cam periphery51 by spring 42. As cam. is rotated, lever 45 is oscillated back andforth to periodically vary the speed of output pinion 25 of transmission40, this pinion driving the bevel gear 20. Thus, the angular velocity ofdisk 10 is correspondingly periodically varied to vary the radialvelocity component of the pellets distributed from the disk ordistributor, so that these pellets are distributed over narrow circularstrips of periodically varying radii to achieve uniform distributionover the selected horizontal cross-sectional area.

Referring more particularly to Figs. 3 and 4, the output worm 34a oftransmission 40 drives a worm wheel 34b secured to a shaft carrying thecam 50 on its outer end. Cam 50 continuously engages the end of a rod 43which is connected to the speed selecting lever 45, so that the speedselecting lever is continuously moved in accordance with the designedperiphery 51 of cam 50. Thus, the speed of output bevel gear 25 iscontinuously varied.

An important feature of the invention is the design of cam 50. Theperiphery 51 of this cam is so designed that the time period duringwhich lever 45 is held at any selected output speed of pinion 25 isproportional to the value of such output speed. Thereby, the periodduring which distributor 10 is maintained at any given angular velocityis dependent upon the value of the angular velocity. Accordingly, withincreasing areas to be covered at increasing radial velocity componentsof the pellets, the time period is such that the distribution of pelletsper unit of area is substantially constant.

The invention distributor and its associated driving arrangement thusachieve a uniform distribution of the pellets over a given horizontalcross-sectional area of a vertically extending zone without the dynamicbalancing and other problems pertinent to involute peripherydistributors.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventionprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. Apparatus for distributing material substantially uni formly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination a centrifugal distribution diskrotatable about a vertical axis substantially centrally of suchcross-sectional area to distribute material in all radial directionsfrom such axis, the peripheral portions of said distributor beingequi-radially distant from its axis of rotation; means operable to feedmaterial to said distributor substantially at its center of rotation;and driving means for rotating said distributor constructed and arrangedto continuously cyclically vary the angular velocity of said distributorto correspondingly vary the radius of distribution of the material; thecircumferential periphery of the upper, material distributing surface ofsaid disk being unobstructed throughout its entire length whereby, whenthe disk is rotated, material is distributed therefrom in all directionsradially of the disk.

2. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a centrifugal distribution diskrotatable about a vertical axis substantially centrally of suchcross-sectional area to distribute material in all radial directionsfrom such axis; means operable to feed material to said disk; anddriving means for rotating said disk constructed and arranged tocontinuously cyclically vary the angular velocity of said disk tocorrespondingly vary the radius of distribution of the material; thecircumferential periphery of the upper, material distributing surface ofsaid disk being unobstructed throughout its entire length whereby, whenthe disk is rotated, material is distributed therefrom in all directionsradially of the disk.

3. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a centrifugal distribution diskrotatable about a vertical axis substantially centrally of suchcross-sectional area to distribute material in all radial directionsfrom such axis; means operable to feed material to said disksubstantially at its center of rotation; and driving means for rotatingsaid disk constructed and arranged to continuously cyclically vary theangular velocity of said disk to correspondingly vary the radius ofdistribution of the material; the circumferential periphery of theupper, material distributing surface of said disk being unobstructedthroughout its entire length whereby, when the disk is rotated, materialis distributed therefrom in all directions radially of the disk.

4. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical axis; means operable to feed material to saiddisk; and driving means for rotating said disk constructed and arrangedto continuously cyclically vary the angular velocity of said disk tocorrespondingly vary the radius of distribution of the material; thecircumferential periphery of the upper, material distributing surface ofsaid disk being unobstructed throughout its entire length whereby, whenthe disk is rotated, material is distributed therefrom in all directionsradially of the disk.

5. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical axis; means operable to feed material to saiddisk substantially at its center of rotation; and driving means forrotating said disk constructed and arranged to continuously cyclicallyvary the angular velocity of said disk to correspondingly vary theradius of distribution of the material; the circumferential periphery ofthe upper, material distributing surface of said disk being unobstructedthroughout its entire length whereby, when the disk is rotated, materialis distributed therefrom in all directions radially of the disk.

6. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical axis; means operable to feed material to saiddisk substantially axially to its apex; a constant speed driving means;a variable speed transmission connecting said driving means to rotatesaid disk; speed selector means for said transmission; and a controlelement driven by said driving means and operatively associated withsaid speed selector means, said control element cyclically operatingsaid speed selector means to periodically vary the angular velocity ofsaid disk.

7. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially "ertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical axis; means operable to feed material to saiddisk substantially axially to its apex; at constant speed motor; avariable speed transmission connecting said motor to rotate said disk;speed selector means for said transmission; and a control element drivenby said motor and operatively associated with said speed selector means,said control element cyclically operating said speed selector means toperiodically vary the angular velocity of said disk.

8. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical axis; means operable to feed material to saiddisk substantially axially to its apex; a constant speed driving means;a variable speed transmission connecting said driving means to rotatesaid disk and having a speed selecting lever; and a rotatable cam drivenat a uniform angular velocity by said motor and engaged with said lever,said cam cyclically positioning said lever to periodically vary theangular velocity of said disk.

9. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical .axis; means operable to feed material tosaid disk substantially axially to its apex; at constant speed drivingmeans; a variable speed transmission connecting said driving means torotate said disk and having a speed selecting lever; and a rotatable camdriven at a uniform angular velocity by said motor and engaged with saidlever, said cam cyclically positioning said lever to periodically varythe angular velocity of said disk; said cam being so constructed andarranged that the time period of the lever at a given angular velocityis proportional to the value of the angular velocity.

10. Apparatus for distributing material substantially uniformly over ahorizontal cross-sectional area of a substantially vertically extendingzone comprising, in combination, a conical centrifugal distribution diskrotatable about a vertical axis; means operable to feed material to saiddisk substantially axially to its apex; a constant speed driving means;:a variable speed transmission connecting said driving means to rotatesaid disk and having a speed selecting lever; and a rotatable cam drivenat a uniform angular velocity by said motor and engaged with said lever,said cam cyclically positioning said lever to periodically vary theangular velocity of said disk; said disk having holes substantially atits axis for flow of material to the center of said cross-sectionalarea.

References Cited in the file of this patent UNITED STATES PATENTS1,764,108 Kennedy June 17, 1930 2,274,172 Swisher Feb. 24, 19422,468,712 Kohler Apr. 26, 1949 2,507,166 Lehman May 9, 1950 2,532,136Zahn Nov. 28, 1950 2,561,258 Wolf July 17, 1951 2,665,118 Broman Jan. 5,1954

